1. Statement of the Technical Field
The inventive arrangements relate to electronic article surveillance tags and more particularly to magnetically controlled locks which are used to secure such tags to articles.
2. Description of the Related Art
Electronic article surveillance systems are well known in the art. These systems utilize EAS tags containing sensor elements that can be detected when moved to a detection zone of an EAS system. The tags are generally attached to merchandise and are either removed or deactivated by store clerks when an authorized person wishes to purchase the item from the secured premises. Several different types of EAS systems are known in the art including magnetic systems, acousto-magnetic systems, radio-frequency systems and microwave type systems. All such systems require an EAS tag to be secured to items which are to be protected by the EAS system.
Conventional electronic article surveillance (EAS) tags often utilize a lock of some type to facilitate securing of the tag to an item of merchandise. Mechanical and magnetic type locks are known and each has benefits and drawbacks. For example, magnetic locks suffer from a common problem which allows the lock to be momentarily unlatched when the tag is impacted upon a hard surface. The amount of force required to cause unlocking is dependent upon the design of the lock, and more particularly upon a spring that is used to retain the lock in a latched condition. Lighter springs exerting less spring force are designed to work with lower strength magnetic detachers and heavier springs exerting more spring force are designed to work with higher strength magnetic detachers. But regardless of spring weight used, the un-authorized unlocking of EAS tags by striking them upon a surface is known problem. The spring which retains the device in a locked condition will compress and the lock will momentarily transition to an unlocked condition.